1. Field of the Invention
In one aspect of the present invention, a protector sleeve is disclosed for protecting a pre-deployed, expandable member in its collapsed state on a catheter. Preferably, the protector sleeve facilitates flushing of a catheter lumen, e.g., a guidewire lumen, and/or immersion of the catheter assembly in a liquid, without exposing the expandable member to the liquid.
2. Description of the Related Art
Angioplasty is an efficient and effective method for opening stenoses in the coronary artery and other parts of the vascular system. Dilatation balloon catheters are used in the treatment. The catheter is positioned at the location of a blockage and a balloon is inflated by supplying a fluid under pressure through an inflation lumen to the balloon, causing stretching of the artery and pressing of the lesion into the artery wall to re-establish acceptable blood flow through the artery.
The profile of the dilatation balloon catheter, which is determined by the outer diameter of the distal end portion of the balloon, is an important characteristic. To move through the artery, the deflated balloon diameter should be as small as possible. The core or inner tube diameter of the catheter should be minimized along with the balloon, which can be done by folding, wrapping or twisting the balloon to achieve the smallest profile possible or by reducing wall thicknesses, to the extent possible, of the balloon itself. This deflated diameter affects the ease and ability of the dilatation catheter to pass through a guide catheter and through the coronary arteries leading to the stenosis to be opened.
In order to keep the outer diameter of the balloon catheter in its deflated condition, it is common to use a balloon protector. A balloon protector protects the balloon and distal tip of the catheter from possible damage during storage and keeps the balloon tightly wrapped in its deflated condition to minimize the outer diameter of the balloon in its deflated state. During the sterilization process, the catheter, with the balloon protector in place, is exposed to an elevated temperature for a period of time which causes the balloon to be heat set in the folded or wrapped configuration in which it is held by the balloon protector. This heat setting of a balloon gives the balloon a memory so that when it is inflated and deflated during an angioplasty procedure, the deflation will cause the balloon to return to its tightly wrapped heat set shape. This heat set shape will give the balloon a low profile diameter which will help when moving the catheter to a new stenosis or removal of the catheter after the procedure has been performed.
Some current balloon protectors are tubular units made of TEFLON, the inner diameter varying along the length of the tube so as to provide adequate compression at both the proximal and distal cones, the marker band area, and remaining areas of the balloon. These TEFLON balloon protectors may be made by heat shrinking a TEFLON tube down around a mandrel, resulting in a protector having some variability in size. A problem with such protectors is that in combination with the inherent variability in balloon size in any group of catheters, the variance in the balloon protector may be large enough that all the balloon protectors will not fit any given catheter; the protector must instead be individually selected from the group to fit the catheter.
During some interventional procedures, it is desirable to flush the interior of a catheter with liquids that may provide lubrication, or procedure specific actions such as anti-coagulation. These liquids may be applied with a syringe, with or without, a needle attached. Typical fluid application can be from distal to proximal, or proximal to distal depending on the type of catheter or operator preference.
Oftentimes, fluid enters the space between the catheter and the balloon protector through capillary action of the liquid. Capillary action is the attraction of the surface of a liquid to the surface of a solid, which either elevates or depresses the liquid depending upon molecular surface forces. Capillary action is a physical effect caused by the interactions of a liquid with the walls of a thin tube. The capillary effect is a function of the ability of the liquid to wet a particular material. One gets the same effect for pores and narrow spaces in any hydrophilic object. A narrow tube coated with a hydrophobic substance (such as TEFLON) should not show a capillary effect.
Balloons maybe damaged when the exterior balloon area of a catheter comes in contact with a fluid before deployment. Wetting may occur when systems are submerged in a liquid prior to deployment and/or when the catheter is flushed with liquids prior to deployment. Tools used during flushing may also contact the balloon area and either damage the balloon or damage and/or dislodge devices attached to the balloon.
Thus, there is a need for a simple protector sleeve for protecting an expandable member mounted on a catheter from damage due to exposure to moisture during pre-deployment handling.
In one embodiment, a protector sleeve is disclosed for protecting a radially collapsed expandable member mounted along a distal end portion of a catheter which has an inner lumen. The protector sleeve comprises a tubular member having proximal and distal portions The proximal portion is adapted to slidably engage the distal end portion of the catheter and cover the collapsed expandable member, wherein a coaxial separation between the proximal portion of the tubular member and the collapsed expandable member is sized to substantially prevent liquids from entering the coaxial separation. The distal portion of the tubular member defines a passageway adapted to fluidly couple with the inner lumen of the catheter, such that the inner lumen may be flushed with a liquid while the collapsed expandable member remains substantially dry.
In a variation to the above-described invention, the tubular member of the protector sleeve is made from a material selected from the group consisting of TEFLON, silicones, parylene, and other hydrophobic materials known in the art.
The tubular member may be tapered along the distal portion. The proximal portion of the tubular member is preferably longer than the collapsed expandable member. Further, the tubular member preferably has an inner surface that is coated with a hydrophobic material. In one aspect, the tubular member may be chemically modified to repel water molecules.
In one preferred mode of the protector sleeve, the proximal and distal portions of the tubular member are made from a single continuous material. The tubular member may also comprise a seal between the proximal and distal portions.
The tubular member and the seal may be formed by extrusion. Alternatively, the tubular member and the seal may be molded.
The collapsed expandable member for which the protector sleeve is designed to protect may comprise an inflatable balloon in a radially collapsed state. Alternatively, the collapsed expandable member may comprise an expandable stent in a radially collapsed state. Alternatively, the collapsed expandable member may comprise an expandable stent or graft mounted over an expansion actuator, such as an inflatable balloon.
In another preferred embodiment of the present invention, a protector sleeve is disclosed for protecting an expandable member on a catheter having an inner lumen and a distal tip, wherein the expandable member is in a collapsed state prior to deployment. The protector sleeve comprises a tubular member having proximal and distal portions and a sealing member therebetween. The proximal portion is adapted to slidably engage the catheter and cover the collapsed expandable member, wherein a coaxial separation between the proximal portion of the tubular member and the collapsed expandable member is sized to substantially prevent liquids from entering the coaxial separation. The sealing member is adapted to engage the distal tip of the catheter, such that a substantially fluid-tight seal is created between the sealing member and the distal tip. The distal portion of the tubular member defines a passageway adapted to fluidly couple with the inner lumen of the catheter, such that the inner lumen may be flushed with a liquid while the collapsed expandable member proximal to the sealing member remains substantially dry.
The sealing member may comprise an elastomer seal. Further, the proximal and distal portions of the tubular member and the sealing member may be formed from a single continuous material. Preferably, the distal portion of the tubular member is sufficiently long to prevent a flushing device from contacting the distal tip of the catheter.
The protector sleeve is preferably used where the collapsed expandable member comprises an inflatable balloon in a radially collapsed state. Alternatively, the collapsed expandable member may comprise a expandable stent in a radially collapsed state. Alternatively, the collapsed expandable member may comprise an expandable stent or graft mounted over an expansion actuator, such as an inflatable balloon.
Also disclosed is a method for protecting an expandable member mounted on a catheter having an inner lumen and a distal tip, wherein the expandable member is in a collapsed state prior to deployment. The method comprises providing a protector sleeve comprising a tubular member having proximal and distal portions and a sealing member therebetween, wherein the sealing member is adapted to engage the distal tip of the catheter, such that a substantially fluid-tight seal is created between the sealing member and the distal tip, and wherein the distal portion of the tubular member defines a passageway adapted to fluidly couple with the inner lumen of the catheter, such that the inner lumen may be flushed with a liquid while the collapsed expandable member proximal to the sealing member remains substantially dry. The protector sleeve is slid over the collapsed expandable member, such that the distal tip of the catheter engages the sealing member.
In one preferred variation to the disclosed method, a portion of a flushing device may be inserted into the passageway of the distal portion. The inner lumen of the catheter may then be flushed.
In another variation of the protector sleeve, a pre-deployment protector sleeve is disclosed for protecting a soluble polymeric coating applied to a portion of a catheter having an inner lumen and a distal tip. The protector sleeve comprises a tubular member having proximal and distal portions and a sealing member therebetween. The proximal portion is adapted to slidably engage the catheter and cover the polymeric coating, wherein a coaxial separation between the proximal portion of the tubular member and the polymeric coating is sized to substantially prevent liquids from entering the coaxial separation. The sealing member is adapted to engage the distal tip of the catheter, such that a substantially fluid-tight seal is created between the sealing member and the distal tip. The distal portion of the tubular member defines a passageway adapted to fluidly couple with the inner lumen of the catheter, such that the inner lumen may be flushed with a liquid while the polymeric coating proximal to the sealing member remains substantially dry.
The pre-deployment protector sleeve described above may be used for assemblies in which the soluble polymeric coating covers an expandable member mounted on the catheter.
The pre-deployment protector sleeve may also be used where the soluble polymeric coating further comprises a bioactive substance.